1. Field of the Invention
The present invention relates to an image reading device, an image reading method, and a non-transitory computer-readable medium.
2. Description of the Related Art
In an image reading device including a reading unit that reciprocates in the sub-scanning direction to optically read an image of an original, the reading unit extending in the main scanning direction sometime becomes skewed (titled) with respect to the main scanning direction. A technology for detecting the quantity of a skew using a sensor has already been known.
Japanese Unexamined Patent Application Publication No. H5-328050 discloses an image reading device including a filler (flag) provided to the reading unit and enabling the position of the reading unit to be detected, and a sensor for detecting the filler. According to the disclosure of Japanese Unexamined Patent Application Publication No. H5-328050, the skew quantity (inclination angle) of the reading unit is detected based on the amount of change in the filler length detected by the sensor as the filler travels across the sensor.
In Japanese Unexamined Patent Application Publication No. H5-328050, in order to improve the skew quantity detection accuracy, the length of the filler needs to be extended, and therefore, the size of the device becomes increased, disadvantageously. Furthermore, in Japanese Unexamined Patent Application Publication No. H5-328050, the sensor lacks the capability of detecting the direction in which the reading unit is skewed, that is, whether the reading unit is tilted in a positive direction or a negative direction.